Butylated cresol preparation



Oct. 13, 1970 M. HEss.

BUTYLATED CRESOL PREPARATION 2 Sheets-Sheet l Filed Feb. 6, 1967 INVENTOR. MART/N HESS Oct. 13, 1970 I M. HEss 3,534,111

BUTYLATED CRESOL PREPARATION Filed Feb. e, 19e? 2 sheets-sheet a mcREsoL pcREsaL /50-BUTYLENE CA TA LYST 1 BASE l SEPA RA TE MUIVOBUTYL DI'BUTYL'CRESOLS CRESLS D'Bl/TYL META CRESOL TFA/VS'A/.KYL TE D/-BI/TYL 7 l SEPARATE l-Qof-BUTYLfCR/ssoLsljmms-Amrum' cATA/.Ysr L (HEAT) l.. 1

0/'5UTYL PAPA TESOL FIG. 3

I NVEN TOR.

'MA E T/N H555 bilig/Lf nited States Patent 1015@ 3,534,111 Patented Oct. 13, 1970 U.S. Cl. 260-624 5 Claims ABSTRACT OF THE DISCLOSURE The joint preparation of di-butyl-para-cresol and mono-butyl-meta-cresol is carried out by a process which virtually eliminates any isobutylene polymer production and any loss of starting material due to the production of other undesirable butylated cresol products. The process involves the butylation of a mixture of metaand para-cresol to an extent below complete di-alkylation, the separation of di-butyl-para-cresol therefrom followed by a traus-alkylation reaction between the produced di-butylmeta-cresol, mono-butyl-para-cresol and mono-butylmeta-cresol to give di-butyl-para-cresol and mono-butylmeta-cresol. The di-butyl-para-cresol is a well-known antioxidant and the mono-butyl-meta-cresol also having antioxidant properties is a valuable intermediate in the production of commercial antioxidants and stabilizers.

BACKGROUND OF THE INVENTION Cresols, as mixtures of three isomers, are readily obtained from coal tar. The ortho-cresol is separated `from the metaand para-isomers of the mixture by distillation because the ortho-isomer has a boiling point suiciently different from the boiling points of the metaand paraisomers. The metaand para-cresols, however, are not separable from each other by distillation because of the closeness of their boiling points. This fact leads to the use of mixtures of metaand para-cresol in alkylation reactions to produce the valuable butylated cresol products, mono-butyl-meta-cresol (2tbutylS-methylphenol) and di-butyl-para-cresol (2,6-di-t-butyl-4-methylphenol). Since mixtures of metaand para-cresols are used in commercial alkylation processes, substantial quantities of both the undesirable mono-butyl-para-cresol (2-t-butyl- 4-methylphenol) and the undesirable di-butyl-meta-cresol (2,4-di-t-butyl-S-methylphenol) are produced, these compounds being of little commercial value. These undesirable compounds substantially decrease the yields of the desired mono-butyl-meta-cresol and di-butyl-para-cresol. L

While the undesired di-butyl-rneta-cresol is separable from di-butyl-para-cresol by distillation, the mono-butylpara-cresol distills at a temperature that is too close to the distillation temperature of =monobutylmetacresol to be separated practically by distillation.

In the Stevens patent, U.S. 2,206,924, a process is disclosed for the complete di-alkylation of metaand paracresol mixtures. The desirable di-butyl-para-cresol is separated yfrom the undesirable di-butyl-meta-cresol by distillation. This undesired di-butyl-meta-cresol is mixed with a metaand para-cresol mixture and then treated with acid to dealkylate the di-butyl-meta-cresol and alkylate the cresols to a mixture of mono-butyl-cresols and other reaction products. Then those mono-butyl-cresols are separated by distillation.

The Stevens process requires the complete di-alkylation of the starting \meta-, para-cresol mixture. This complete di-alkylation results in substantial loss of isobutylene through polymer formation. Also, the dealkylation of the di-butyl-meta-cresol with a meta, para-cresol mixture to produce the desired mono-butyl-meta-cresol poses difculties. Preferably, relatively pure meta-cresol is used so that no undesired mono-butyl-para-cresol is produced. As is well known, the separation of pure meta-cresol from para-cresol is extremely ditiicult, but if a mixture of metaand para-cresol is used, significant quantities of the undesirable mono-butyl-para-cresol will result.

SUMMARY OF THE INVENTION The process of this invention utilizes a mixture of metaand para-cresols for the production of mono-butylmeta-cresol and di-butyl-para-cresol and does not result in significant polymerization of isobutylene during the alkylation reaction. Accordingly, the process utilizes, nearly quantitatively, the initial meta, para-cresol feed stock, and the isobutylene. Possible side reactions, in-

e cluding polymerization, are kept at a low level and are almost negligible. The process limits the production of undesired mono-butyl-para-cresol in a mono-butyl-metacresol mixture to any desired level and eliminates the need for a separate dealkylation step for di-butyl-meta-cresol. Also, considerable economic benets are derived through the use of the process of this invention because Of increased production capacity, decreased labor costs, and decreased utility costs through improved thermodynamic eiciency.

In accordance with the present invention, a mixture of metaand para-cresol is alkylated with isobutylene in the presence of an acidic catalyst to an extent less than 85% of the theoretically possible di-alkylation of the product to produce a mixture comprising mono-t-butylmeta-cresol, mono-t-butyl para-cresol, di-t-butyl metacresol and di-t-butyl-para-cresol. The alkylated mixture is neutralized and the monotbutylcresols are separated from the di-t-butyl-cresols by distillation. The di-t-butylcresols are then separated from each other by distillation. The di-t-butyl-para-cresol, the desired product, is removed. The di-t-butyl-meta-cresol is returned to the mixture of mouo-t-butyl-cresols to form a trans-alkylation reaction mixture, and the trans-alkylation reaction mixture heated in the presence of an acidic alkylation catalyst to cause trans-alkylation to produce a mixture of monot-butyl-meta-cresol and di-t-butyl-para-cresol. This transalkylation reaction mixture is then neutralized and the mono-t-butyl-meta-cresol and di-t-butyl-para-cresol mixture separated as desired products for use.

BRIEF DESCRIPTION OF THE DRAWINGS Apparatus for effecting the process of the invention is schematically illustrated in FIG. 1.

FIG. 2 graphically illustrates the very sharp decline in the eiciency of isobutylene in the alkylation of a commercially available cresol mixture at about 85 percent of complete di-alkylation of such a mixture at 60 C.

FIG. 3 schematically illustrates the invention by means of a ow diagram.

DETAILED DESCRIPTION 'I'he process of the present invention may be more readily understood by reference to FIG. 1, which illustrates schematically apparatus for effecting the process. A mixture of metaand para-cresol is fed to an alkylation reactor 51 through feed line 1. This meta, para-cresol mixture may be Varied according to the desired proportions of mono-butyl-meta-cresol and di-butyl-para-cresol preferred at outputs 39 and 27. An acidic alkylation catalyst is fed to the reactor 51, through feed line 3 and suicient isobutylene added, to give the desired extent of theoretical di-alkylation in the alkylation step, through line 45. After a predetermined time has elapsed during which the desired extent of di-alkylation has occurred in reactor 51, the alkylated mixture is discharged through line 4 into a ueutralizer 71, into which there is also fed,

through line 47, a sufficient amount of sodium hydroxide or other basic material to neutralize the acidic phenolic material and catalyst in the alkylate and prevent decomposition or polymerization of the alkylated product. The alkylation mixture at this time, contains mono-butyl-metacresol, mono-butyl-para-cresol, di-butyl-meta-cresol and di-butyl-para-cresol. The alkylation mixture is discharged from the neutralizer 71 through line 7 and fed to the separator 61, herein illustrated as a distillation column. In separator 61, the di-butyl-cresols are separated as residue from the mono-butylated cresols and discharged through line 11, while the mixture of mono-butyl-paracresol and mono-butyl-meta-cresol with residual unalkylated cresols and isobutylene is discharged as overhead through line 9 and fed to separator 63 which is illustrated herein as a distillation column. The unreacted cresols and residual isobutylene with any minor amounts of polymeric material are discharged from separator 63 as overhead through line 49. The unalkylated cresols, if desired, can be removed from line 49 and fed through recycle line to the initial alkylation step while the undesirable constituents are discharged through line 6. From separator 63, the mono-butyl-cresols are discharged as residue through line 15.

The di-butylated cresols, discharged from separator 61 through line 11, are fed to a separator 65, herein illustrated as a distillation column. The desirable di-butylpara-cresol is Separated as overhead from the mixture through line 27 and handled as desired.

The undesired di-butyl-meta-cresol as residue from separation column 65 then ows by line 17 through valve 81 and is fed to the trans-alkylation reactor 53. At this point, additional di-butyl-meta-cresol may be added.A By way of discharge line from separator 63, the monobutylated cresols are also fed to trans-alkylation reactor 53. Thus, mono-butyl-meta-cresol, mono-butyl-para-cresol and di-butyl-meta-cresol are present in reactor 53. Also added to the trans-alkylation reactor through feed line 19, is sucient acidic alkylation catalyst, such as sulfuric acid. The mixture is heated, whereby the trans-alkylation of di-butyl-meta-cresol and mono-butyl-para-cresol is carried out to produce mono-butyl-meta-cresol and dibutyl-para-cresol. Following a predetermined reaction time, the reaction product is discharged through line to a neutralizer 73 into which there is also fed suflicient sodium hydroxide or other basic material through line 21 to neutralize acidic constituents therein and prevent decomposition or polymerization of the products. The reaction product discharged from neutralizer 73 is then fed by means of line 23 into a separator 67, herein illustrated as a distillation column, for separation of the monoand di-butylated products. The mono-butylated cresols from separator '67 are discharged as overhead through line 25. Generally, the product in line 25 comprises about a ratio of nine parts of mono-butyl-meta-cresol to one part of mono-butyl-para-cresol. This mixture may be discharged through valve 83 and line 26 and handled as desired.

The di-butylated cresols from separator 67 are discharged by way of line 13, through valve 85 to line 43 which feeds the di-butylated cresols by means of line 11 into the separator 65. In separator y65, the di-butyl-paracresol is removed, as the previous di-butyl-para-cresol was removed, through line 27 and handled as desired. The dibutyl-meta-cresol remaining in the separator `65 can then be fed through feed line 17 and recycled through the process.

In another embodiment of the invention, should the mono-butyl-meta-cresol and mono-butyl-para-cresol be desired in a mixture that has a higher percentage of monobutyl-meta-cresol therein, a second stage trans-alkylation reaction is used. Referring again to FIG. 1, if desired, the mono-butyl-meta-cresol and mono-butyl-para-cresol mixture from line 25 is fed by means of valve 83 to a feed line 29 to a second trans-alkylation reactor 55. For the purpose of this second trans-alkylation, a quantity of the di-butyl-meta-cresol from line 17 is fed by means of valve S1 into a feed line 31 to the second trans-alkylation reactor 55. Sufficient acidic alkylation catalyst is fed through line 33. After heating for a predetermined time, the reaction mixture is discharged from the second trans-alkylation reactor through line 34 into a neutralizer 75, into which there is also fed sufcient sodium hydroxide or other neutralizing agent through line 35 to neutralize the acidic constituents in the reaction mixture. The reaction mixture is then discharged through line 37 into separator 69, herein illustrated as a distillation column. In separator 69, the mixture of mono-butylated constituents is removed through discharge line 39, said mixture containing a higher percentage (96-98% or higher) of mono-butyl-metacresol, to be handled as desired. The di-butylated cresols from separator 69 are discharged through line 41 and by means of valve 85 are returned to the di-butyl-cresol recycle line 43 for further separation as previously described.

Liquid phase alkylations, as commercially practiced, consist of dissolving alkylating agent in the reactant to be alkylated in the presence of a catalyst. If a gaseous alkylating agent is used, the gas is dispersed throughout the liquid by agitation or sparging. The alkylating agent is transferred from the gas phase into solution in accordance with the law of mass transfer. As long as sufcient reactive alkyl acceptor material is present in the solution, the alkylating agent exhibits little tendency to polymerize. As alkylation approached completion, by-products, especially polymers, form in increasing amounts.

An essential aspect of the invention is the limitation of the di-alkylation of the meta-, para-cresol mixture in the iirst alkylation reaction step. Contrary to present cornmercial practices, it has now been found that alkylations should not be allowed to approach completion beyond the degree of alkylation required by the nal product mix. Therefore, according to the present invention, the dialkylation of the initial meta, para-cresol mixture is limited to about 85% of the theoretical di-alkylation (after subtracting out the unreacted meta-cresol and paracresol).

The polymerization of isobutylene 0r other alkylating agent is illustrated in FIG. 2, which shows the efficiency of the isobutylene in an alkylation reaction at the percent theoretical alkylation of a reaction mixture. It will ybe noted that the eiciency is fairly stable up until about 70% of the theoretical extent of di-alkylation and, at a point corresponding to of the theoretical extent of d-alkylation, the efficiency decreases at an extraordinarily rapid rate, due to polymerization and by-product formation. It is this tendency to polymerize and form byproducts at the higher percent di-alkylation of an alkylated mixture which causes the loss of products and starting materials. These problems are not present in this process which does not provide for the total di-alkylation of the starting meta-, para-cresol feed stock mixture.

In the alkylation step of the invention, both di-butylisomers and both mono-butyl-isomers are formed. The mixture of di-butyl-cresols is separated from the mixture of mono-butyl-cresols. Then, the di-butyl-cresols are separated from each other. The desired product, di-butyl-paracresol, is retained. The undesired product, the di-butylmeta-cresol, is then combined with the mixture of monobutyl-cresols for the trans-alkylation step. In the transalkylation step, the undesirable di-butyl-meta-cresol is trans-alkylated with the undesired mono-butyl-para-cresol to form the desired mono-butyl-meta-cresol and di-butylpara-cresol.

In the trans-alkylation step, the di-butyl-meta-cresol is trans-alkylated with mono butyl para cresol to form mono butyl meta cresol and di-butyl-para-cresol. Although the exact mechanism of such a trans-alkylation is not fully understood, it is probable that one t-butyl group of the di-butyl-metal-cresol is removed by the acidic catalyst and the system is activated to an extent which causes this group to attack the mono-butyl-para-cresol and thus form di-butyl-para-cresol. The reactivities of the various reactants are such that di-butyl-para-cresol is formed at the expense of di-butyl-meta-cresol and that desirable products are formed from the undesirable products in the initial mixture.

The initial alkylation reaction can be carried out according to any of the well-known methods of the prior art. The only limitation being that the alkylation be stopped before about 85% of the theoretical di-alkylation of the cresols has occurred.

The alkylated mixture is then neutralized and the products separated as previously described before effecting the trans-alkylation step. A preferable separation would be to effect the removal of the di-butyl-paracresol and feed the entire remaining mixture to a trans-alkylation reactor.

In the process of this invention, the trans-alkylation is carried out using a catalytic amount of an acidic alkylation catalyst. The amount of catalyst used is generally about 0.025 to by weight of the cresolic mixture `being subjected to trans-alkylation. If less than about 0.025 of the catalyst is used, the alkylation is slow. For economic reasons, there is no advantage to using greater than 10 weight percent of catalyst although no adverse effects due to process would be attained thereby.

It is preferred to use temperatures during the transalkylation process in the order of about 50-125 C. If temperatures below about 50 C. are used, the reaction is sluggish and time-consuming. Temperatures in excess of 125 C. are found to be disadvantageous because of the increased side reactions and the tendency for polymerization to occur in the reaction mass.

It is preferable to use sulfuric acid as the alkylation catalyst, however, other acidic catalysts such as other mineral acids, such as phosphoric acid, perchloric acid, Friedel-Crafts catalysts, aryl and alkyl sulfonic acids, such as benzenesulfonic acid, phenolsulfonic acid, phenoldisulfonic acid, and the like, in addition to other alkylation catalysts known in the art may be used in the process.

The reaction is carried out at pressures ranging from sub-atmospheric or atmospheric pressure up to about 3,000 p.s.i.g. From the standpoint of equipment costs, the use of low pressures is most desirable. However, positive pressures up to about 3,000 p.s.i.g. may be used although it is obviously advantageous for economic reasons to run the reaction at the lowest convenient pressure.

The trans-alkylation reaction time may Ibe conveniently determined by sampling the reaction mixture and determining the composition of the samples by vapor phase chromatography or other analytic methods.

The reaction is conveniently carried out in the absence of a solvent although, if desired, any solvent which is inert to the reactants and the catalysts under the conditions of the reaction can be employed. Suitable such solvents include benzene, toluene, xylene, tetralin, decalin, hexane, heptane, cyclohexane, and the like.

Th operation can be carried out batch-wise or continuously as desired. Unreacted starting materials and catalysts are readily recycled for use in a subsequent run.

The process of the invention is further illustrated by the following examples.

EXAMPLE I A feed mixture containing 100 moles of mixed meta-, and para-cresol are fed to the alkylation reactor. The feed was a commercial commodity and was found by analysis to consist of 67.0% meta-cresol and 33.0% paracresol. The mixture was alkylated under atmospheric pressure at a temperature of 70 C. in the presence of isobutylene and using sulfuric acid as catalyst. After 9 hours reaction time, at which point, excluding unreacted metacresol and para-cresol, the mixture was di-alkylated to an extent of 68.5% of the theoretical possible di-alkylation,

as defined below. The product was neutralized with sodium hydroxide and an analysis of the product gave the following:

Product: Moles Meta-cresol 2.5

Para-cresol 0.5

Di-butyl-para-cresol 19.0 Di-butyl-meta-cresol 17.0 Mono-butyl-metal-cresol 47.5 Mono-butyl-para-cresol 13.5

The 68.5 di-alkylation is a value determined by calculating the total amount of alkylation of the mixture, after substracting the value of unreacted cresols, and thus computing the value of theoretical di-alkylation. For example, in the experiment, di-butyl-para-cresol (19), and di-butyl-meta-cresol (17) comprise 36 moles of actual dialkylated product. Also, tlie mono-butyl-para-cresol (13.5) and mono-butyl-meta-cresol (47.5) are equal to 61 moles of mono-alkylated product, which, divided by two (6l/2 or 30.5), is equal to 30.5 moles of theoretical di-alkylation. Thus, the sum of theoretical di-alkylation, 66.5 (364-305), with relation to the actual alkylated product, 97 moles (100 moles-3 moles of recovered cresols) is equal to 66.5/97 or 68.5% theoretical dialkylation.

The meta, para-cresols were removed from the reaction mixture by distillation. These cresol isomers came off as overhead and were held for possible recycle to the alkylation reaction where another quantity of cresol was to be alkylated.

After the metaand para-cresol isomers which boil at about 1Z0-123 C. at 50 mm. mercury pressure had been removed, the temperature was raised to 14S-155 C. to remove the mono-butyl-cresol isomers. Then, the temperature was raised to 16S-175 C. and the di-butylpara-cresol was removed as overhead and sent to processing as desired. The temperature was raised again to C. and the di-butyl-meta-cresol removed as overhead. The bottoms remaining in the distillation vessel were discarded.

The mono-butyl isomers; namely, mono-butyl-metacresol and mono-butyl-para-cresol, and the undesired dibutyl isomer, di-butyl-meta-cresol, were mixed and fed to a trans-alkylation reactor. In order to provide an excess of di-butyl-meta-cresol, 40 moles of this were added to the mixture being sent to the trans-alkylation reactor and about 0.5% by weight of the sulfuric acid catalyst based on the Weight of the cresol isomers was added to the total mixture. The butylated cresol feed to the transalkylation reactor was thus:

Feed: Moles Mono-butyl-meta-cresol 47.5 Mono-butyl-para-cresol 13.5 Di-butyl-meta-cresol 57.0 Di-butyl-para-cresol 0.0

After 5 hours in the trans-alkylation reactor, at 85 C., and atmospheric pressure the reaction mixture was removed from the trans-alkylation reactor and neutralized. Analysis of the product by vapor-phase chromatography showed the product to contain:

Product: Moles Mono-butyl-meta-cresol 57.6 Monobutyl-paracresol 3.4 Di-butyl-meta-cresol 46.9 Dibutylparacresol 10.1

The mono-butylated cresols were separated from the di-butylated cresols by distillation. This yielded 61 moles of a mono-butylated cresol fraction, which fraction analyzed to be 94.4% mono-butyl-meta-cresol with 5.6% mono-butyl-para-cresol as impurity. The di-butylated fraction was subjected to a further distillation to yield an additional 10.1 moles of di-butyl-para-cresol, the desired product. The remaining 46.9 moles of di-butyl-metacresol is used for recycle in the subsequent alkylations.

Thus, from 100 moles of mixed cresols, there were produced 29.1 moles of di-butyl-paraacresol and 61 moles of 96% pure mono-butyl-meta-cresol.

In this example, the first alkylation was carried out to an extent slightly in excess of that necessary for a continuous recycle process. As can be seen from the nal product, 6.9 moles of excess di-butyl-meta-cresol remain. This excess can be readily controlled, however, by alkylating to a slightly less extent in subsequent alkyations and a continuous process provided where no excess di-butyl-metacresol is produced.

EXAMPLE II The process of the invention was carried out to obtain a higher proportion of the desired product, mono-butylmeta-cresol. To this end, the process of Example I was carried out with the desire to produce a mono-butylated cresol mixture having a higher percentage of mono-butylmeta-cresol. The process of Example I was varied in that a larger amount of di-butyl-meta-cresol was added to the trans-alkylation reactor. Following the alkylation in Example I, the product containing the proportion of mono- -butylated and di-butylated cresols describedy in Example I was fed to the trans-alkylation reactor and, instead of the 40 moles of additional di-butyl-meta-cresol of Example I, 80 moles were added for this example. Thus, the feed to the trans-alkylation reactor, in addition to the sulfuric acid catalyst, is as follows:

Compound: Moles Di-butyl-para-cresol y0.0 Mono-butyl-meta-cresol 47.5 Di-butyl-meta-cresol 97.0 Mono-butyl-para-cresol 13.5

Following the trans-alkylation procedure of Example I, the resulting product analyzed:

Product: Moles Di-butyl-para-cresol 11.3 Di-butylmetacresol 85.7 Mono-butyl-meta-cresol 58.8 Mono-butyl-para-cresol 2.2

Therefore, starting with 100 moles of mixed meta, para-cresol feed stock, there was produced 30.3 moles of di-butyLpara-cresol and 61 moles of mono-butyl-cresols containing 96.5% mono-butyl-meta-cresol.

It will be noted that in this instance as compared with Example I, the equilibrium value was changed in that greater amounts of di-butyl-para-cresol and mono-butylrneta-cresol were produced, and less amounts of di-butylmeta-cresol and mono-butylparacresol were produced.

EXAMPLE III To the reactor Was added a mixture which was comprised of 1419.5 grams of meta-cresol and 710 grams of para-cresol. There was also added 9.3 grams of concentrated sulfuric acid catalyst. A recycle from a previous run and consisting of meta-cresol 79.3 grams, and paracresol 16.5 grams was added to the reactor. The mass was heated under atmospheric pressure to a temperature of 80 C. and 1475.2 grams of isobutylene was slowly added. After an interval of time, found to give 63.3% of the theoretical possible dialkylation, the reaction was stopped and the product discharged. The product was neutralized with 3.8 grams of sodium hydroxide. The product mixture was found to contain 1683.4 grams of mono-butylmeta-cresol, 518.1 grams of mono-butyl-pararesol, 637.9 grams of di-butyl-meta-cresol, 751.1 grams of di-butylpara-cresol, 16.5 grams of para-cresol, 79.3 grams of metacresol, and only 15.1 grams of by-products, such as polymers. A fraction consisting of 2201.5 grams of mixed mono-butylated products was removed by distillation. Also, 1389 grams of di-butylated products were removed by distillation. The mono-butylated cresols were combined with additional di-butyl-metacresol, to give a total of 9292.8 grams of di-butyl-meta-cresol, and fed to a trans-alkylation reactor. Also added to the reactor was sulfuric acid, 28.7 grams as catalyst. After 3.5 hours at 90 C. and atmospheric pressure, the trans-alkylation product was discharged and neutralized with 11.7 grams of sodium hydroxide. The product was found to comprise 2157.5 grams of mono-butyl-meta-cresol, 44.0 grams of mono-butyl-para-cresol, 8656.8 grams of di-butyl-rnetacresol and 636.0 grams of di-butyl-para-cresol. The product was sent to a distillation column where the monobutyl-cresol mixture comprising 2201.5 grams of mixed mono-butyl-cresols having a mono-butyl-meta-cresol content of about 98% was removed. Then, the di-butyl-cresols comprising 865 6.8 grams of di-butyl-meta-cresol and 636.0 grams of di-butyl-para-cresol were removed. These di-butylated cresols were combined with the di-butylated cresols that had been obtained from the initial alkylation. The two isomers were separated by distillation. The dibutyl-para-cresol obtained Was 1387.2 grams of desired di-butylated product. The di-butyl-meta-cresol obtained was 9292.8 grams and Was ready for recycle to the transalkylation step for subsequent reactions. The initial amount of added dibutyl-metacresol is reused indefinitely to carry out the trans-alkylation while the desired monobutyl-meta-cresol and di-butyl-para-cresol is removed.

EXAMPLE IV The procedure of Example III was repeated until the step of trans-alkylation was reached. The procedure was then varied in that a double trans-alkylation was carried out to produce a monobutylated cresol mixture having a higher percentage of mono-butyl-meta-cresol. At the initial trans-alkylation, 2201.5 grams of mixed mono-butylcresols (1683.4 grams of mono-butyl-meta-cresol and 518.1 grams of mono-butyl-para-cresol), 1399 grams of dibutyl-meta-cresol, and 9.0 grams of sulfuric acid catalyst were added to the reactor. After sufficient time for the trans-alkylation, the product mixture was discharged and neutralized with 3.7 grams of sodium hydroxide. The neutralized mixture contained 1981.4 grams of mono-butylmeta-cresol, 220.2 grams of mono-butyl-para-cresol, 999.3 grams of dibutylmetacresol, and 399.7 grams of dibutyl-para-cresol. The product was sepaarted by distillation into a di-butylated cresol fraction and a monobutylated fraction. The mono-butylated cresol fraction (2201.5 grams) was fed to a second trans-alkylation reactor. Also added to the fraction was 3449.9 grams of dibutyl-meta-cresol and suliicient sulfuric acid catalyst. Following 4 hours at 80 C. and atmospheric pressure, the product was discharged from the reactor and neutralized with Sodium hydroxide. The product contained 2156 grams of mono-butyl-meta-cresol, 44 grams of monobutyl-fpara-cresol, 3213.9 grams of di-butyl-meta-cresol and 236.1 grams of di-butyl-para-cresol. By distillation, the mono-butyl-cresol mixture (2200 grams) was removed as a 98% pure mono-butylmetacresol, the desired product. The di-butylated cresol fraction was combined with the di-butylated cresols from the initial alkylation reaction and fed to a distillation column where 1387.2 grams of di-butyl-para-cresol were recovered for use as the desired product. The di-butyhmeta-cresol that was recovered is useable for recycle. There is thus presented a process wherein no additional di-butyl-meta-cresol need be supplied and the valuable di-butyl-para-cresol and monobutyl-meta-cresol products are provided from commercial meta, para-cresol mixtures.

I claim:

l. A process for treating the product resulting from the reaction of a mixture of metaand para-cresols with isobutylene to an extent less than of the theoretical possible dialkylation of said cresols in the presence of an acid catalyst, which product is a mixture of mono-butylmeta-cresol, mono-butyl-para-cresol, di-butyl-meta-cresol, and di-butyl-para-cresol, in order to recover greater amounts of mono-butyl-meta-cresol and di-butyl-paracresol than exist in said product, the process comprising the steps of:

(a) distilling said product into a rst fraction comprised of said mono-butyl-cresols, and into a second fraction comprised of said di-butyl-cresols;

(b) distilling said second fraction into said di-butylmeta-cresol and into said di-butyl-para-cresols;

(c) adding said di-butyl-meta-cresol to said rst fraction to form a transalkylation mixture;

(d) heating said transalkylation mixture to a temperature of about 50-125 C. in the presence of an alkylation catalyst to cause transalkylation to convert said mono-butyl-para-cresol and said di-butyl-meta-cresol to a transalkylation product comprising as major constituents, mono-butyl-meta-cresol, and di-butylpara-cresol, di-butyl-meta-cresol, and as a minor constituent, mono-butyl-para-cresol;

(e) neutralizing said transalkylation product;

(f) distilling said transalkylation product into a third fraction comprised of said mono-butylated cresols and into a fourth fraction comprised of said di-butylpara-cresol and di-butyl-meta-cresol;

(g) distilling said fourth fraction into di-butyl-paracresol and into di-butyl-meta-cresol.

2. The process of claim 1 wherein said di-butyl-metacresol from said fourth fraction is recycled to the transalkylation reaction for further trans-alkylation.

3. The process of claim 1 including:

(a) adding additional di-butyl-meta-cresol to said third fraction to form a second trans-alkylation mixture;

(b) contacting said second mixture with an acidic alkylation catalyst at a temperature of about 50-l25 C. to convert the mono-butyl-para-cresol and dibutyl-meta-cresol to a third mixture having as its major constituents, di-butyl-meta-cresol, di-butyl-paracresol and mono-butyl-meta-cresol and having as a minor constituent, mono-butyl-para-cresol;

(c) neutralizing said third mixture; and

(d) separating said third mixture into a mono-butylated cresol component and di-butylated cresol component.

4. The process for producing mono-butyl-meta-cresol and di-butyl-para-cresol comprising:

(a) alkylating a mixture of meta-cresol and para-cresol with isobutylene to an extent less than 85% of the theoretical possible dialkylation of said cresols by contacting said mixture With isobutylene in the presence of an acidic alkylation catalyst to form a rst mixture of di-butyl cresols and mono-butyl cresols;

(b) neutralizing said first mixture with an aqueous alkali solution;

(c) distilling said first mixture into a rst monobutylated cresol fraction and a second di-butylated cresol fraction;

(d) distilling the di-butyl-meta-cresol portion of said second fraction from the di-butyl-para-cresol;

(e) combining said di-butyl-meta-cresol with said first fraction to form a transalkylation mixture;

(f) heating said transalkylation mixture to a temperature of about 50-125 C. with an acidic alkylation catalyst for a period of time to produce a product comprising mono-butyl-meta-cresol, di-butyl-paracresol and di-butyl-meta-cresol as a major constituent and mono-butyl-para-cresol as a minor constituent;

(g) neutralizing said product with an aqueous alkali solution; and

(h) distilling said product into a di-butyl-meta-cresol and di-butyl-para-cresol fraction and a mono-butylmeta-cresol and mono-butyl-para-cresol fraction.

5. The process for producing mono-butyl-meta-cresol and di-butyl-para-cresol comprising:

(a) alkylating a mixture of meta-cresol and para-cresol With isobutylene to an extent less than 85% of the theoretical possible dialkylation of said cresols to form a first mixture of di-butyl-cresols and monobutyl-cresols;

(b) neutralizing said first mixture with an aqueous alkali solution;

(c) distilling di-butyl-para-cresol from said rst mixture to leave a fraction containing di-butyl-metacresol and mono-butyl-cresol;

(d) adding to said fraction an acidic alkylation catalyst to form a transalkylation mixture;

(e) heating said transalkylation mixture to a temperature of about 50-125 C., for a period of time to produce a product comprising mono-butyl-metacresol, di-butyl-para-cresol, and di-butyl-meta-cresol as major constituents and mono-butyl-para-cresol as a minor constituent; and

(f) neutralizing said product.

References Cited UNITED STATES PATENTS 2,206,924 7/ 1940 Stevens et al. 2,297,588 9/ 1942 Stevens et al. 2,802,884 8/ 1957 DAlelio.

FOREIGN PATENTS 1,145,629 3/1963 Germany.

BERNARD HELFIN, Primary Examiner 0 W. B. LONE, Assistant Examiner U.S. Cl. X.R. 260-621 

